Model comparison
GPT-5.5 Pro vs Mistral Small 3.1
GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 31.4 on the Noometry Index. Mistral Small 3.1 costs 168× less per token, which makes it the better buy when GPT-5.5 Pro's lead doesn't matter for your workload.
Last verified . 4 shared benchmarks.
Mistral AISummary
- They share 4 benchmarks with published results for both. GPT-5.5 Pro scores higher in 3 categories and Mistral Small 3.1 in 0 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in math, where GPT-5.5 Pro leads 83.8 to 13.7.
- The biggest single-benchmark swing is OTIS Mock AIME 2024-2025: 100% for GPT-5.5 Pro and 3.9% for Mistral Small 3.1.
- Mistral Small 3.1 is cheaper at $0.35 / $0.56 per million input/output tokens, against $30 / $180 for GPT-5.5 Pro.
- GPT-5.5 Pro accepts more context: 1.05M tokens versus 128K.
- Mistral Small 3.1 has downloadable open weights; the other is API-only.
Side by side
| GPT-5.5 Pro | Mistral Small 3.1 | |
|---|---|---|
| Provider | OpenAI | Mistral AI |
| Noometry Index | 64.3 | 31.4 |
| Released | 2026-04-23 | 2025-03-17 |
| Weights | Proprietary | Open |
| Context window | 1.05M | 128K |
| Max output | 128K | 102K |
| Input $ / M tokens | $30 | $0.35 |
| Output $ / M tokens | $180 | $0.56 |
| Results tracked | 14 | 28 |
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Category by category
Coding Not comparable
GPT-5.5 Pro: —, Mistral Small 3.1: 37.7 (#175)
| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| LMArena Coding | — | 1309 |
Reasoning GPT-5.5 Pro leads
GPT-5.5 Pro: 73.6 (#7), Mistral Small 3.1: 18.9 (#249)
| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| Chess Puzzles | 64% | 1% |
| Epoch Capabilities Index | 162.45 | 127.48 |
| ARC-AGI-2 | 84.6% | — |
| SimpleBench | 76.9% | — |
| ARC-AGI-1 | 96.5% | — |
| CritPt | 30.6% | — |
| LMArena Hard Prompts | — | 1278 |
| DTBench | 96% | — |
| LMCA | 53.9% | — |
Math GPT-5.5 Pro leads
GPT-5.5 Pro: 83.8 (#8), Mistral Small 3.1: 13.7 (#295)
| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| OTIS Mock AIME 2024-2025 | 100% | 3.9% |
| FrontierMath (Tiers 1-3) | 87.7% | — |
| FrontierMath Tier 4 | 78% | — |
| Omni-MATH | — | 24.8% |
| LMArena Math | — | 1261 |
| FrontierMath (Feb 2025 set) | 52.4% | — |
| FrontierMath Tier 4 (v1) | 39.6% | — |
Knowledge GPT-5.5 Pro leads
GPT-5.5 Pro: 64.2 (#17), Mistral Small 3.1: 22.6 (#266)
| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| GPQA Diamond | 93.9% | 41.9% |
| MMLU-Pro | — | 61% |
| GPQA (HELM) | — | 39.2% |
| LMArena Expert | — | 1258 |
Multimodal Not comparable
GPT-5.5 Pro: —, Mistral Small 3.1: 32.6 (#93)
| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| LMArena Vision | — | 1136 |
Multilingual Not comparable
GPT-5.5 Pro: —, Mistral Small 3.1: 41.4 (#204)
| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| LMArena Non-English | — | 1255 |
| LMArena Chinese | — | 1254 |
| LMArena French | — | 1270 |
| LMArena German | — | 1266 |
| LMArena Japanese | — | 1210 |
| LMArena Korean | — | 1206 |
| LMArena Russian | — | 1263 |
| LMArena Spanish | — | 1283 |
Instruction Following Not comparable
GPT-5.5 Pro: —, Mistral Small 3.1: 63.8 (#225)
| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| IFEval | — | 75% |
| LMArena Instruction Following | — | 1264 |
Long Context Not comparable
GPT-5.5 Pro: —, Mistral Small 3.1: 39.5 (#172)
| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| LMArena Longer Query | — | 1300 |
Writing & Preference Not comparable
GPT-5.5 Pro: —, Mistral Small 3.1: 37.2 (#254)
| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| LMArena Text | — | 1278 |
| LMArena Creative Writing | — | 1253 |
| EQ-Bench Creative Writing | — | 761 |
| WildBench | — | 78.8% |
| LMArena Multi-Turn | — | 1270 |
Frequently asked questions
Is GPT-5.5 Pro better than Mistral Small 3.1?
GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 31.4 on the Noometry Index. Mistral Small 3.1 costs 168× less per token, which makes it the better buy when GPT-5.5 Pro's lead doesn't matter for your workload.
Which is cheaper, GPT-5.5 Pro or Mistral Small 3.1?
Mistral Small 3.1 is cheaper. It lists at $0.35 per million input tokens and $0.56 per million output tokens; GPT-5.5 Pro lists at $30 and $180.
Which has the bigger context window?
GPT-5.5 Pro does, with 1.05M tokens against 128K.
How many benchmarks do GPT-5.5 Pro and Mistral Small 3.1 share?
4 benchmarks have published results for both models. GPT-5.5 Pro has 14 scored results on Noometry and Mistral Small 3.1 has 28.